Bacterial vaginosis (BV) is the most prevalent cause of symptomatic vaginal discharge in women. Its etiology is unknown, however, it is characterized by displacement of the normal lactobacillus-predominant vaginal flora with large numbers of anaerobic and facultatively anaerobic bacteria. These changes do not appear to be all-or-none, but instead abnormal vaginal flora can be viewed as a continuum of change. Microbiological changes can be quantified by using a standardized interpretative methods for vaginal fluid Gram stains. Epidemiologic associations exist between BV and sexually transmitted diseases (STDs) including human immunodeficiency virus (HIV), however cause and effect are unknown. One hypothesis is that without "protective" lactobacilli, women with abnormal vaginal flora (BV) are at increased risk of acquiring an STD upon exposure. The specific aims of this proposal are to determine the impact of BV on the acquisition of STDs by conducting prospective studies of women at high risk for STD. These studies represent continuation and extension of our ongoing work in this area. We will conduct a randomized controlled trial of treatment versus placebo for women with symptomatic BV. The women will be followed for a total of one year with serial examinations with the study outcome being acquisition of STD. In addition, we will utilize information and specimens obtained from these women to investigate issues related to the pathogenesis of abnormal vaginal flora, including the relationships of behaviors to changes in flora and description of the immunological factors associated with the patterns of vaginal flora and symptomatology in each of the three groups of women.